Changes in English @ Weblate

None String updated in the repository cnp3-ebook / principles/network — English	English The third technique to compute forwarding tables is to rely on a control plane using a distributed algorithm. Routers exchange control messages to discover the network topology and build their forwarding table based on them. We dedicate a more detailed description of such distributed algorithms later in this section. English 318 characters edited Current translation Read only The third technique to compute forwarding tables is to rely on a control plane using a distributed algorithm. Routers exchange control messages to discover the network topology and build their forwarding table based on them. We dedicate a more detailed description of such distributed algorithms later in this section. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English In networks that rely on source routing, hosts use control packets to automatically discover the best path(s). In addition to the source and destination addresses, `control packets` contain a list that records the intermediate nodes. This list is often called the `record route` because it allows recording the route followed by a given packet. When a node receives such a `control packet`, it first checks whether its address is included in the record route. If yes, the packet has already been forwarded by this node and it is silently discarded. Otherwise, it adds its own address to the `record route` and forwards the packet to all its interfaces, except the interface over which the packet has been received. Thanks to this, the `control packet` can explore all paths between a source and a given destination. English 815 characters edited Current translation Read only In networks that rely on source routing, hosts use control packets to automatically discover the best path(s). In addition to the source and destination addresses, `control packets` contain a list that records the intermediate nodes. This list is often called the `record route` because it allows recording the route followed by a given packet. When a node receives such a `control packet`, it first checks whether its address is included in the record route. If yes, the packet has already been forwarded by this node and it is silently discarded. Otherwise, it adds its own address to the `record route` and forwards the packet to all its interfaces, except the interface over which the packet has been received. Thanks to this, the `control packet` can explore all paths between a source and a given destination. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English In the network above, router `R2` is attached to two outgoing links. `R2` is connected to both `R1` and `R3`. `R2` can easily determine that it is connected to these two nodes by exchanging packets with them or observing the packets that it receives over each interface. Assume for example that when a node (either host or router) starts, it sends a special control packet over each of its interfaces to advertise its own address to its neighbors. When a node receives such a packet, it automatically replies with its own address. This exchange can also be used to verify whether a neighbor, either router or host, is still alive. With `source routing`, the data plane packets include a list of identifiers. This list is called a `source route`. It indicates the path to be followed by the packet as a sequence of link identifiers. When a node receives such a `data plane` packet, it first checks whether the packet's destination is a direct neighbor. In this case, the packet is forwarded to this neighbor. Otherwise, the node extracts the next address from the list and forwards it to the neighbor. This allows the source to specify the explicit path to be followed for each packet. For example, in the figure above there are two possible paths between `A` and `B`. To use the path via `R2`, `A` would send a packet that contains `R1,R2,R3` as source route. To avoid going via `R2`, `A` would place `R1,R3` as the source route in its transmitted packet. If `A` knows the complete network topology and all link identifiers, it can easily compute the source route towards each destination. It can even use different paths, e.g. for redundancy, to reach a given destination. However, in a real network hosts do not usually have a map of the entire network topology. English 1764 characters edited Current translation Read only In the network above, router `R2` is attached to two outgoing links. `R2` is connected to both `R1` and `R3`. `R2` can easily determine that it is connected to these two nodes by exchanging packets with them or observing the packets that it receives over each interface. Assume for example that when a node (either host or router) starts, it sends a special control packet over each of its interfaces to advertise its own address to its neighbors. When a node receives such a packet, it automatically replies with its own address. This exchange can also be used to verify whether a neighbor, either router or host, is still alive. With `source routing`, the data plane packets include a list of identifiers. This list is called a `source route`. It indicates the path to be followed by the packet as a sequence of link identifiers. When a node receives such a `data plane` packet, it first checks whether the packet's destination is a direct neighbor. In this case, the packet is forwarded to this neighbor. Otherwise, the node extracts the next address from the list and forwards it to the neighbor. This allows the source to specify the explicit path to be followed for each packet. For example, in the figure above there are two possible paths between `A` and `B`. To use the path via `R2`, `A` would send a packet that contains `R1,R2,R3` as source route. To avoid going via `R2`, `A` would place `R1,R3` as the source route in its transmitted packet. If `A` knows the complete network topology and all link identifiers, it can easily compute the source route towards each destination. It can even use different paths, e.g. for redundancy, to reach a given destination. However, in a real network hosts do not usually have a map of the entire network topology. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English `Data packets` are used to exchange data while `control packets` are used to discover the paths between hosts. With `source routing`, routers can be kept as simple as possible and all the complexity is placed on the hosts. This is in contrast with the previous technique where the nodes had to maintain a port-address and a forwarding table while the hosts simply sent and received packets. Each node is configured with one unique address and there is one identifier per outgoing link. For simplicity and to avoid cluttering the figures with those identifiers, we assume that each node uses as link identifiers north, west, south,... In practice, a node would associate one integer to each outgoing link. English 704 characters edited Current translation Read only `Data packets` are used to exchange data while `control packets` are used to discover the paths between hosts. With `source routing`, routers can be kept as simple as possible and all the complexity is placed on the hosts. This is in contrast with the previous technique where the nodes had to maintain a port-address and a forwarding table while the hosts simply sent and received packets. Each node is configured with one unique address and there is one identifier per outgoing link. For simplicity and to avoid cluttering the figures with those identifiers, we assume that each node uses as link identifiers north, west, south,... In practice, a node would associate one integer to each outgoing link. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English Another technique called `source routing` can be used to automatically compute forwarding tables. It has been used in interconnecting Token Ring networks and in some wireless networks. Intuitively, `source routing` enables a destination to automatically discover the paths from a given source towards itself. This technique requires nodes to encode information inside some packets. For simplicity, let us assume that the `data plane` supports two types of packets : English 465 characters edited Current translation Read only Another technique called `source routing` can be used to automatically compute forwarding tables. It has been used in interconnecting Token Ring networks and in some wireless networks. Intuitively, `source routing` enables a destination to automatically discover the paths from a given source towards itself. This technique requires nodes to encode information inside some packets. For simplicity, let us assume that the `data plane` supports two types of packets : 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English Assume that the network has started and all port-address and forwarding tables are empty. Host `A` sends a packet towards `B`. Upon reception of this packet, `R1` updates its port-address table. Since `B` is not present in the port-address table, the packet is broadcasted. Both `R2` and `R3` receive a copy of the packet sent by `A`. They both update their port-address table. Unfortunately, they also both broadcast the received packet. `B` receives a first copy of the packet, but `R3` and `R2` receive it again. `R3` will then broadcast this copy of the packet to `B` and `R1` while `R2` will broadcast its copy to `R1`. Although `B` has already received two copies of the packet, it is still inside the network and continues to loop. Due to the presence of the cycle, a single packet towards an unknown destination generates many copies of this packet that loop and will eventually saturate the network. Network operators who are using port-address tables to automatically compute the forwarding tables also use distributed algorithms to ensure that the network topology is always a tree. English 1093 characters edited Current translation Read only Assume that the network has started and all port-address and forwarding tables are empty. Host `A` sends a packet towards `B`. Upon reception of this packet, `R1` updates its port-address table. Since `B` is not present in the port-address table, the packet is broadcasted. Both `R2` and `R3` receive a copy of the packet sent by `A`. They both update their port-address table. Unfortunately, they also both broadcast the received packet. `B` receives a first copy of the packet, but `R3` and `R2` receive it again. `R3` will then broadcast this copy of the packet to `B` and `R1` while `R2` will broadcast its copy to `R1`. Although `B` has already received two copies of the packet, it is still inside the network and continues to loop. Due to the presence of the cycle, a single packet towards an unknown destination generates many copies of this packet that loop and will eventually saturate the network. Network operators who are using port-address tables to automatically compute the forwarding tables also use distributed algorithms to ensure that the network topology is always a tree. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English Host `A` sends a packet towards `B`. When receiving this packet, `R1` learns that `A` is reachable via its `West` interface. Since it does not have an entry for destination `B` in its port-address table, it forwards the packet to both `R2` and `R3`. When `R2` receives the packet, it updates its own forwarding table and forward the packet to `C`. Since `C` is not the intended recipient, it simply discards the received packet. Router `R3` also receives the packet. It learns that `A` is reachable via its `North-West` interface and broadcasts the packet to `R4` and `R5`. `R5` also updates its forwarding table and finally forwards it to destination `B`. Let us now consider what happens when `B` sends a reply to `A`. `R5` first learns that `B` is attached to its `North-East` port. It then consults its port-address table and finds that `A` is reachable via its `North-West` interface. The packet is then forwarded hop-by-hop to `A` without any broadcasting. Later on, if `C` sends a packet to `B`, this packet will reach `R1` that contains a valid forwarding entry in its forwarding table. English 1095 characters edited Current translation Read only Host `A` sends a packet towards `B`. When receiving this packet, `R1` learns that `A` is reachable via its `West` interface. Since it does not have an entry for destination `B` in its port-address table, it forwards the packet to both `R2` and `R3`. When `R2` receives the packet, it updates its own forwarding table and forward the packet to `C`. Since `C` is not the intended recipient, it simply discards the received packet. Router `R3` also receives the packet. It learns that `A` is reachable via its `North-West` interface and broadcasts the packet to `R4` and `R5`. `R5` also updates its forwarding table and finally forwards it to destination `B`. Let us now consider what happens when `B` sends a reply to `A`. `R5` first learns that `B` is attached to its `North-East` port. It then consults its port-address table and finds that `A` is reachable via its `North-West` interface. The packet is then forwarded hop-by-hop to `A` without any broadcasting. Later on, if `C` sends a packet to `B`, this packet will reach `R1` that contains a valid forwarding entry in its forwarding table. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English To understand the operation of the port-address table, let us consider the example network shown in the figure below. This network contains three hosts: `A`, `B` and `C` and five routers, `R1` to `R5`. When the network boots, all the forwarding tables of the nodes are empty. English 275 characters edited Current translation Read only To understand the operation of the port-address table, let us consider the example network shown in the figure below. This network contains three hosts: `A`, `B` and `C` and five routers, `R1` to `R5`. When the network boots, all the forwarding tables of the nodes are empty. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English Networks deployed several techniques to update the forwarding tables upon the arrival of a packet. In this section, we briefly present the principles that underlie three of these techniques. English 190 characters edited Current translation Read only Networks deployed several techniques to update the forwarding tables upon the arrival of a packet. In this section, we briefly present the principles that underlie three of these techniques. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English Similarly, routers also fail. There are two types of failures that affect routers. A router may stop forwarding packets due to hardware or software problems (e.g., due to a crash of its operating system). A router may also need to be halted from time to time (e.g., to upgrade its operating system or to install new interface cards). These planned and unplanned events affect the set of links and routers that can be used to forward packets in the network. Still, most network users expect that their network will continue to correctly forward packets despite all these events. With manually computed forwarding tables, it is usually impossible to pre-compute the forwarding tables while taking into account all possible failure scenarios. English 739 characters edited Current translation Read only Similarly, routers also fail. There are two types of failures that affect routers. A router may stop forwarding packets due to hardware or software problems (e.g., due to a crash of its operating system). A router may also need to be halted from time to time (e.g., to upgrade its operating system or to install new interface cards). These planned and unplanned events affect the set of links and routers that can be used to forward packets in the network. Still, most network users expect that their network will continue to correctly forward packets despite all these events. With manually computed forwarding tables, it is usually impossible to pre-compute the forwarding tables while taking into account all possible failure scenarios. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English In most networks, manual forwarding tables are not a solution for two reasons. First, most networks are too large to enable a manual computation of the forwarding tables. Second, with manually computed forwarding tables, it is very difficult to deal with link and router failures. Networks need to operate 24h a day, 365 days per year. Many events can affect the routers and links that compose a network. Link failures are regular events in deployed networks. Links can fail for various reasons, including electromagnetic interference, fiber cuts, hardware or software problems on the terminating routers,... Some links also need to be either added to or removed from the network because their utilization is too low or their cost is too high. English 743 characters edited Current translation Read only In most networks, manual forwarding tables are not a solution for two reasons. First, most networks are too large to enable a manual computation of the forwarding tables. Second, with manually computed forwarding tables, it is very difficult to deal with link and router failures. Networks need to operate 24h a day, 365 days per year. Many events can affect the routers and links that compose a network. Link failures are regular events in deployed networks. Links can fail for various reasons, including electromagnetic interference, fiber cuts, hardware or software problems on the terminating routers,... Some links also need to be either added to or removed from the network because their utilization is too low or their cost is too high. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English The computation of the forwarding tables of all the routers inside a network is a key element for the correct operation of the network. This computation can be carried out by using either distributed or centralized algorithms. These algorithms provide different performance, may lead to different types of paths, but their composition must lead to valid paths. English 360 characters edited Current translation Read only The computation of the forwarding tables of all the routers inside a network is a key element for the correct operation of the network. This computation can be carried out by using either distributed or centralized algorithms. These algorithms provide different performance, may lead to different types of paths, but their composition must lead to valid paths. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English The network layer enables the transmission of information between hosts that are not directly connected through intermediate routers. This transmission is carried out by putting the information to be transmitted inside a data structure which is called a `packet`. As a frame that contains useful data and control information, a packet also contains both data supplied by the user and control information. An important issue in the network layer is the ability to identify a node (host or router) inside the network. This identification is performed by associating an address to each node. An :term:`address` is usually represented as a sequence of bits. Most networks use fixed-length addresses. At this stage, let us simply assume that each of the nodes in the above network has an address which corresponds to the binary representation of its name on the figure. English 864 characters edited Current translation Read only The network layer enables the transmission of information between hosts that are not directly connected through intermediate routers. This transmission is carried out by putting the information to be transmitted inside a data structure which is called a `packet`. As a frame that contains useful data and control information, a packet also contains both data supplied by the user and control information. An important issue in the network layer is the ability to identify a node (host or router) inside the network. This identification is performed by associating an address to each node. An :term:`address` is usually represented as a sequence of bits. Most networks use fixed-length addresses. At this stage, let us simply assume that each of the nodes in the above network has an address which corresponds to the binary representation of its name on the figure. 2 years ago
None String updated in the repository cnp3-ebook / principles/network — English	English Even if we only consider the point-to-point datalink layers, there is an important characteristic of these layers that we cannot ignore. No datalink layer is able to send frames of unlimited size. Each datalink layer is characterized by a maximum frame size. There are more than dozen different datalink layers and unfortunately most of them use a different maximum frame size. This heterogeneity in the maximum frame sizes will cause problems when we will need to exchange data between hosts attached to different types of datalink layers. English 540 characters edited Current translation Read only Even if we only consider the point-to-point datalink layers, there is an important characteristic of these layers that we cannot ignore. No datalink layer is able to send frames of unlimited size. Each datalink layer is characterized by a maximum frame size. There are more than dozen different datalink layers and unfortunately most of them use a different maximum frame size. This heterogeneity in the maximum frame sizes will cause problems when we will need to exchange data between hosts attached to different types of datalink layers. 2 years ago
None Resource update cnp3-ebook / principles/naming — English	File `locale/pot/principles/naming.pot` was added. 2 years ago
None String updated in the repository cnp3-ebook / principles/naming — English	English Until February 2008, the root DNS servers only had IPv4 addresses. IPv6 addresses were slowly added to the root DNS servers to avoid creating problems as discussed in http://www.icann.org/en/committees/security/sac018.pdf As of February 2021, there remain a few DNS root servers that are still not reachable using IPv6. The full list is available at http://www.root-servers.org/ English 378 characters edited Current translation Read only Until February 2008, the root DNS servers only had IPv4 addresses. IPv6 addresses were slowly added to the root DNS servers to avoid creating problems as discussed in http://www.icann.org/en/committees/security/sac018.pdf As of February 2021, there remain a few DNS root servers that are still not reachable using IPv6. The full list is available at http://www.root-servers.org/ 2 years ago
None String updated in the repository cnp3-ebook / principles/naming — English	English Names provide a lot of flexibility compared to addresses. For the network, they play a similar role as variables in programming languages. No programmer using a high-level programming language would consider using hardcoded values instead of variables. For the same reasons, all networked applications should depend on names and avoid dealing with addresses as much as possible. English 378 characters edited Current translation Read only Names provide a lot of flexibility compared to addresses. For the network, they play a similar role as variables in programming languages. No programmer using a high-level programming language would consider using hardcoded values instead of variables. For the same reasons, all networked applications should depend on names and avoid dealing with addresses as much as possible. 2 years ago
None String updated in the repository cnp3-ebook / principles/naming — English	English Mapping a single name onto a set of addresses allows popular servers to dynamically scale. There are also benefits in mapping multiple names, possibly a large number of them, onto a single address. Consider the case of information servers run by individuals or SMEs. Some of these servers attract only a few clients per day. Using a single physical server for each of these services would be a waste of resources. A better approach is to use a single server for a set of services that are all identified by different names. This enables service providers to support a large number of servers processes, identified by different names, onto a single physical server. If one of these server processes becomes very popular, it will be possible to map its name onto a set of addresses to be able to sustain the load. There are some deployments where this mapping is done dynamically in function of the load. English 902 characters edited Current translation Read only Mapping a single name onto a set of addresses allows popular servers to dynamically scale. There are also benefits in mapping multiple names, possibly a large number of them, onto a single address. Consider the case of information servers run by individuals or SMEs. Some of these servers attract only a few clients per day. Using a single physical server for each of these services would be a waste of resources. A better approach is to use a single server for a set of services that are all identified by different names. This enables service providers to support a large number of servers processes, identified by different names, onto a single physical server. If one of these server processes becomes very popular, it will be possible to map its name onto a set of addresses to be able to sustain the load. There are some deployments where this mapping is done dynamically in function of the load. 2 years ago
None String updated in the repository cnp3-ebook / principles/naming — English	English Using names solves these problems and provides additional benefits. If the clients are configured with the name of the server, they will query the name service before contacting the server. The name service will resolve the name into the corresponding address. If a server process needs to move from one physical server to another, it suffices to update the name to address mapping on the name service to allow all clients to connect to the new server. The name service also enables the servers to better sustain the load. Assume a very popular server which is accessed by millions of users. This service cannot be provided by a single physical server due to performance limitations. Thanks to the utilization of names, it is possible to scale this service by mapping a given name to a set of addresses. When a client queries the name service for the server's name, the name service returns one of the addresses in the set. Various strategies can be used to select one particular address inside the set of addresses. A first strategy is to select a random address in the set. A second strategy is to maintain information about the load on the servers and return the address of the less loaded server. Note that the list of server addresses does not need to remain fixed. It is possible to add and remove addresses from the list to cope with load fluctuations. Another strategy is to infer the location of the client from the name request and return the address of the closest server. English 1483 characters edited Current translation Read only Using names solves these problems and provides additional benefits. If the clients are configured with the name of the server, they will query the name service before contacting the server. The name service will resolve the name into the corresponding address. If a server process needs to move from one physical server to another, it suffices to update the name to address mapping on the name service to allow all clients to connect to the new server. The name service also enables the servers to better sustain the load. Assume a very popular server which is accessed by millions of users. This service cannot be provided by a single physical server due to performance limitations. Thanks to the utilization of names, it is possible to scale this service by mapping a given name to a set of addresses. When a client queries the name service for the server's name, the name service returns one of the addresses in the set. Various strategies can be used to select one particular address inside the set of addresses. A first strategy is to select a random address in the set. A second strategy is to maintain information about the load on the servers and return the address of the less loaded server. Note that the list of server addresses does not need to remain fixed. It is possible to add and remove addresses from the list to cope with load fluctuations. Another strategy is to infer the location of the client from the name request and return the address of the closest server. 2 years ago
None String updated in the repository cnp3-ebook / principles/naming — English	English In addition to being more human friendly, using names instead of addresses inside applications has several important benefits. To understand them, let us consider a popular application that provides information stored on servers. This application involves clients and servers. The server provides information upon requests from client processes. A first deployment of this application would be to rely only on addresses. In this case, the server process would be installed on one host and the clients would connect to this server to retrieve information. Such a deployment has several drawbacks : English 596 characters edited Current translation Read only In addition to being more human friendly, using names instead of addresses inside applications has several important benefits. To understand them, let us consider a popular application that provides information stored on servers. This application involves clients and servers. The server provides information upon requests from client processes. A first deployment of this application would be to rely only on addresses. In this case, the server process would be installed on one host and the clients would connect to this server to retrieve information. Such a deployment has several drawbacks : 2 years ago

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